Pneumatic power systems are used in a variety of applications, and particularly with regard to tools. Traditionally, pneumatic tools have been designed to be connected to a source of compressed air, such as a stationary air compressor. More recently, portable pressure sources have been developed by which a small vessel containing a pressurised fluid, such as carbon dioxide, may be connected via a regulator to a tool. These systems allow the tools to be used in a more portable fashion without being restricted by the long hosing requirements of conventional set ups.
In this type of portable device, the mass of fluid stored in the vessel in order to power the device must be sufficient for a practical number of operations, but not so large that portability suffers unduly. As a result, it may be necessary to change the portable canisters, or re-fill them relatively often.
Other examples of pneumatic devices (generally referred to as a “motion transfer devices”) may be a hammer drill, jack hammer, grinder, nail gun or paintball gun, or any other device known to be driven pneumatically.
For these portable pneumatic applications, preferably, the driving fluid is carbon dioxide, which is inexpensive and non flammable. Further, carbon dioxide may be stored in the liquid phase at attainable pressure, thereby allowing for a larger mass to be stored within a limited space. In cases where carbon dioxide is used, this means that at room temperature, the vessel will preferably contain both liquid and gaseous carbon dioxide, (at a pressure of typically 750 psi or thereabouts for example).
It should be appreciated that the driving fluid may not be carbon dioxide. The driving fluid could be any other fluid with properties suited to the particular application. However, due to potential venting of the apparatus to atmosphere, it is highly preferred that the driving fluid is non-flammable.
Traditionally, there are two types of filling systems for filling a small portable pressure vessel with a fluid like carbon dioxide for example. Firstly, there are large scale filling plants that invariably use a high pressure pump to force the carbon dioxide into the portable pressure vessel (while maintaining a safe vapour space above the liquefied CO2 in the small canister). These systems are typically closed, and do not allow any gas to escape to the atmosphere.
The second type of system is typically used on a smaller scale, where the portable canisters are filled onsite for example. In these situations, a larger pressurised CO2 bottle is used to fill smaller portable pressure vessels. In this type of setup, the filling is done entirely manually by opening and closing the respective bottle valves until the desired weight of the portable canister is achieved. The driving force to transfer the CO2 comes from the pressure differential and not a pump.
A manual filling system while simple, requires the user to know what they are doing in order to avoid large wastage, and/or dangerous overfill conditions as well as achieving sufficient fill weight.
The present method and apparatus provides a semi-autonomous system that is small and portable and goes at least some way to mitigating one or more of the above problems or at least provides a useful choice.
In this specification where reference has been made to patent specifications, other external documents, or other sources of information, this is generally for the purpose of providing a context for discussing the features of the invention. Unless specifically stated otherwise, reference to such external documents is not to be construed as an admission that such documents, or such sources of information, in any jurisdiction, are prior art, or form part of the common general knowledge in the art.